夜间增温条件下免耕对农田土壤碳氮矿化的影响

发布时间：2019-06-18 17:02

【摘要】：全球变暖对农田生态系统的元素物质转化与循环具有重要影响。以往的研究主要从全天平均温度的升高进行模拟,且大多集中在农田生态系统的地上作物部分。另外,免耕作为一项保护性耕作措施对农作物生长以及土壤碳氮转化过程具有积极作用。那么,在未来温度升高情景下免耕能否改善农田土壤碳氮转化过程从而保持农田生产力的可持续性,对缓解我国的粮食安全问题具有积极意义。本试验针对这一问题,采用田间开放式增温结合免耕处理研究夜间增温条件下免耕对农田土壤碳、氮矿化过程及相关酶活性的影响,探索长期夜间增温及免耕条件下农田土壤碳、氮转化过程对外源碳、氮添加的响应特征。试验设置四个处理:常温+翻耕(CK)、增温+翻耕(W)、常温+免耕(NT)、增温+免耕(WNT)。主要得到以下结论:(1)这四种试验土壤在3种N添加(无N、NH4+-N和NO3--N)条件下,分别在5℃、10℃、15℃、20℃、25℃和30℃温度下进行好氧培养。研究表明:与对照(CK)相比,W处理显著提高了土壤有机碳矿化速率,增幅为5.3%～18.4%; NT处理下有机碳矿化速率增幅显著高于W处理,增幅为14.6%～36.7%; WNT处理下碳矿化速率达到最大值,相比于对照(CK)矿化速率增幅为19.5%～56.7%。施加不同形态氮条件下土壤有机碳矿化的温度敏感性响应特征不同,铵态氮的添加使4种供试土壤的Q10值提升了 3.9%～4.7%;硝态氮的添加对Q10值则无明显影响,对碳矿化速率影响不显著。(2)与CK处理相比,W处理下土壤净氮矿化速率和硝化速率分别增加了31%和8.5%。NT处理下净氮矿化速率的增幅高于W处理,平均提高了 33.9%;但硝化速率降低了 23.7%。与NT处理变化一致,WNT处理下土壤净氮矿化速率提高了 73.8%,硝化速率降低了 17%。与无N添加处理相比,铵态氮添加条件下4个处理土壤的净氮矿化量增加了 4.2～17.7 mg·kg~(-1),硝化量增加了8.1～25.0mg·kg~(-1)。相应地,氮添加使氮矿化和硝化速率都有不同程度的提高,净氮矿化速率分别提高了 18.3%、26.3%、54.6%、53.4%,硝化速率分别提高了84.2%、161.7%、207.0%、140.0%。(3)四种试验土壤在2种C处理(无C、添加C)条件下,分别在5℃℃、10℃、15℃、20℃、25℃和30℃温度下进行好氧培养。研究表明:碳添加条件下CK、W、NT以及WNT处理的净氮矿化速率分别下降了 38.9%、38.9%、43.1%和46.7%,硝化速率则分别下降了 39.8%、38%、40.5%和43.5%。(4) 土壤酶活性对增温及免耕处理的响应不同。随着培养温度(5～30℃)的升高,脲酶、脱氢酶和过氧化氢酶的活性均有不同程度地增强。其中,W处理下脲酶活性的整个培养温度平均值与CK处理相比,提高了 11.5%; NT处理和WNT处理则分别提高了 17.7%和21.2%。CK 土壤在培养温度为5～30℃条件下脱氢酶活性范围为0.5μL/(g·6h) ～ 5.9μL/(g·6h);与CK 土壤相比,W 土壤、NT 土壤和WNT 土壤的整个培养温度平均值分别提高了 18.2%,9.1%和22.7%。CK 土壤在培养温度为5～30℃条件下过氧化氢酶活性范围为5.0mg/(g·h)～5.4mg/(g·h); 4个试验处理对该酶活性的整个培养温度平均值没有明显影响。综上所述,夜间增温、免耕以及夜间增温叠加免耕措施都促进了有机碳、氮矿化过程,提高了有机碳氮的矿化速率,但免耕措施降低了土壤硝化速率和硝化量。因此,在全球变暖的背景下采取免耕措施促进土壤有机氮的矿化过程,提高了铵氮供应量,以满足作物对氮素的需求,同时减缓了硝化过程,减少了氮流失的风险,可能是一项有潜力的可持续应对气候变暖的农业措施。
[Abstract]:Global warming has an important effect on the transformation and circulation of elements in the farmland ecosystem. Previous studies have been mainly simulated from the increase of the average temperature of the whole day, and most of them are concentrated on the above-ground crop part of the farmland ecosystem. In addition, no-tillage as a protective farming measure has a positive effect on the growth of crops and the transformation of soil carbon and nitrogen. In the future, no-tillage can improve the soil carbon-nitrogen conversion process in the farmland so as to keep the agricultural productivity sustainable, and it is of positive significance to alleviate the problem of food security in China. In view of this problem, the effects of no-tillage on carbon, nitrogen mineralization and the activity of the related enzymes under the condition of no-tillage on the soil carbon, nitrogen mineralization and the activity of the related enzymes under the condition of no-tillage in the field were studied in the field of open-ended temperature-increasing and no-tillage treatment, and the carbon and nitrogen conversion processes of the soil under the condition of long-term night-temperature and no-tillage were explored, and the carbon and nitrogen in the field The response characteristics of nitrogen addition. The test is to set four treatments: normal temperature + turn-on (CK), temperature-increasing + turning-up (W), normal-temperature + no-tillage (NT), temperature-increasing + no-tillage (WNT). The following conclusions were obtained: (1) The four test soils were cultured at 5 鈩，

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